Enhancing Odor Analysis with Gas Chromatography-Olfactometry (GC-O): Recent Breakthroughs and Challenges.

Gas chromatography-olfactometry (GC-O) has made significant advancements in recent years, with breakthroughs in its applications and the identification of its limitations. This technology is widely used for analyzing complex odor patterns. The review begins by explaining the principles of GC-O, including sample preparation, separation methods, and olfactory evaluation techniques. It then explores the diverse range of applications where GC-O has found success, such as food and beverage industries, environmental monitoring, perfume and aroma development, and forensic analysis. One of the major breakthroughs in GC-O analysis is the improvement in separation power and resolution of odorants. Techniques like rapid GC, comprehensive two-dimensional GC, and multidimensional GC have enhanced the identification and quantification of odor-active chemicals. However, GC-O also has limitations. These include the challenges in detecting and quantifying trace odorants, dealing with matrix effects, and ensuring the repeatability and consistency of results across laboratories. The review examines these limitations closely and discusses potential solutions and future directions for improvement in GC-O analysis. Overall, this review presents a comprehensive overview of the recent advances in GC-O, covering breakthroughs, applications, and limitations. It aims to promote the wider usage of GC-O analysis in odor analysis and related industries. Researchers, practitioners, and anyone interested in leveraging the capabilities of GC-O in analyzing complex odor patterns will find this review a valuable resource. The article highlights the potential of GC-O and encourages further research and development in the field.

Development of the gas chromatography/mass spectrometry-based aroma designer capable of modifying volatile chemical compositions in complex odors.

Many volatile organic compounds (VOCs) are used to produce various commercial products with aromas mimicking natural products. The VOCs responsible for aromas have been identified from many natural products. The current major strategy is to analyze chemical compositions and aroma qualities of individual VOCs using gas chromatography/mass spectrometry (GC/MS) and GC-olfactometry. However, such analyses cannot determine whether candidate VOCs contribute to the characteristic aroma in mixtures of many VOCs. In this study, we developed a GC/MS-based VOC collection/omission system that can modify the VOC compositions of samples easily and rapidly. The system is composed of GC/MS with a switching unit that can change gas flow routes between MS and a VOC collection device. We first applied this system to prepare gas samples for omission tests, and the aroma qualities of VOC mixtures with and without some VOCs were evaluated by panelists. If aroma qualities were different between the 2 samples, the omitted VOCs were likely key odorants. By collecting VOCs in a gas bag attached to the collection device and transferring some VOCs to MS, specific VOCs could be omitted easily from the VOC mixture. The system could prepare omission samples without chemical identification, preparation of each VOC, and laborious techniques for mixing VOCs, thus overcoming the limitations of previous methods of sample preparation. Finally, the system was used to prepare artificial aromas by replacing VOC compositions between different samples for screening of key odorants. In conclusion, the system developed here can improve aroma research by identifying key odorants from natural products.

Association between flavor composition and sensory profile in thermally processed mandarin juices by multidimensional gas chromatography and multivariate statistical analysis.

Thermal pasteurization decreases the sensory quality of mandarin juice. Flavor composition was determined in four fresh-squeezed and heat-processed mandarin juice varieties using molecular sensory science approaches. The relationships between odorants and sensory profiles were analyzed, and markers for flavor deterioration were screened by multivariate statistical analysis. Seventy-four volatiles were identified, among which 36 odorants with flavor dilution factors ranging from 2 to 128 were detected by multidimensional gas chromatography-mass spectrometry/olfactometry (MDGC-MS/O) coupled with aroma extract dilution analysis (AEDA). Higher intensities of cooked and off-flavor notes were observed in the heated mandarin juice, which was related to the concentration changes of the methional, methanethiol, dimethyl sulfide, and carbon disulfide by partial least squares (PLS) analysis. Ten potential markers (methional, methanethiol, dimethyl sulfide, hydrogen sulfide, ß-damascenone, camphene, trans-ß-ionone, decanal, d-limonene, and α-pinene) were responsible for the sensory discrimination of fresh-squeezed and heated mandarin juices.

Characterization of the key aroma compounds in soy sauce by gas chromatography-mass spectrometry-olfactometry, headspace-gas chromatography-ion mobility spectrometry, odor activity value, and aroma recombination and omission analysis.

Most previous studies on volatile compounds in soy sauce were performed by gas chromatography-mass spectrometry (GC-MS). In this study, the volatile compounds of high-salt liquid-state fermentation soy sauce (HLFSS) were analyzed qualitatively and quantitatively by GC-MS and headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS). One hundred and seventy-four substances were detected using the two instruments, 87 by HS-GC-IMS and 127 by GC-MS. Aldehydes (26), ketones (28), esters (29), and alcohols (26) were the main compounds in HLFSS. In addition, ethyl pyruvate, (E)-2-pentenal and diethyl propanedioate were detected by HS-GC-IMS, which were previously not detected in HLFSS. Forty-eight aromatics including 34 key ones were identified by gas chromatography-olfactometry. Phenylacetaldehyde, methional, 2-methylbutanal, 1-octen-3-ol, ethyl acetate, 2-ethyl-4-hydroxy-5-methyl-3(2H)-furanone, 4-hydroxy-2,5-dimethyl-3(2H)-furanone and 4-ethyl guaiacol were identified as the main aroma compounds in HLFSS by aroma recombination and omission test. This study laid foundation for developing flavor assessment standards for soy sauce.

Volatile flavour identification and odour complexity of radix Angelicae sinensis by electronic nose, integrated gas chromatography-mass spectrometry/olfactometry and comprehensive two-dimensional gas chromatography-time-of-flight-mass spectrometry.

INTRODUCTION: Radix Angelicae sinensis (Danggui, DG) is known as one of the typical traditional Chinese medicines. DG material consists of a variety of volatile substances, polysaccharides, organic acids, ceramides, amino acids, vitamins, microelements, among others, and thus has been used for medicinal and edible purposes in a long history. The fragrance is of importance to assessing the DG material quality. OBJECTIVES: This study was to determine volatile flavour compositions of DG materials and to reveal the odour complexity. MATERIAL AND METHODS: Electronic nose (E-nose), integrated gas chromatography-mass spectrometry/olfactometry (GC-MS/O) and comprehensive two-dimensional gas chromatography-time-of-flight-mass spectrometry (GC × GC-TOF-MS), combined with solid-phase micro-extraction (SPME), were mainly used to address the flavour complexity of DG materials. RESULTS: Using the E-nose sensor responses, a total of 105 batches of DG samples cultivated in six provinces of China were categorised according to their odour differentiations, and a principal component analysis (PCA) model was established for evaluating the sample quality through a combination of Hotelling's T2 and Q-residual values in a statistical quantitative sense. By the GC-MS/O and GC × GC-TOF-MS analyses, 196 volatile flavour compounds were identified, 51 odour-active areas discerned and 39 odourants determined. It was terpenes and aromatics of the flavour compounds that mainly contributed to the odour attributes of DG herb. CONCLUSION: The SPME-GC × GC-TOF-MS method was the first time employed to analyse the volatile flavours of DG materials, and thus made a breakthrough in determining 196 flavour compounds, much more than those in any previous report. The work also made a significant step forward to link the flavour compositions and odour complexity of radix Angelicae sinensis by E-nose and GC-MS/O techniques. It not only provided a statistical PCA model that did not depend on any predetermined compositions or sensory properties for, but also a comprehensive insight into the quality evaluation of DG materials.

Identification of aroma active compounds in walnut oil by monolithic material adsorption extraction of RSC18 combined with gas chromatography-olfactory-mass spectrometry.

A novel extraction method of volatile aroma compounds (VACs) from walnut oil (WO) using monolithic material adsorption extraction (MMSE) was developed herein, and its efficiency was compared with the conventional extraction method based on solid-phase microextraction (SPME) combined with gas chromatography-olfactory-mass spectrometry (GC-O-MS). After protocol optimization of MMSE-RSC18, 77 volatile compounds (38 ones can be sniffed) were extracted from WO, thus having a better performance compared to SPME (56 volatile compounds, 35 ones can be sniffed). Subsequently, based on flavor dilution factors (FDs), odor activity values (OAVs), and recombination and omission experiments, key aroma-active compounds in WO were 1-octen-3-ol (OAV = 82.58), (E)-2-decenal (OAV = 4.10), linalool (OAV = 2.37), γ-dodecalactone (OAV = 2.30), 2-pentylfuran (OAV = 1.62), (E)-2-nonenal (OAV = 1.14) and pentanal (OAV = 1.04). Collectively, compared to HS-SPME, MMSE-RSC18 provided higher capture efficiency of VACs, enabling efficient extraction and analysis of sample aromas.

Variation in Volatile Compounds of Raw Pu-Erh Tea upon Steeping Process by Gas Chromatography-Ion Mobility Spectrometry and Characterization of the Aroma-Active Compounds in Tea Infusion Using Gas Chromatography-Olfactometry-Mass Spectrometry.

Steeping process is an important factor for aroma release of tea, which has rarely been investigated for the aroma changes of raw Pu-erh tea (RAPT). In addition, the comprehensive aroma characteristics identification of RAPT infusion is necessary. In this study, GC-IMS coupled with principal component analysis (PCA) was used to clarify the difference of volatile profiles during the steeping process of RAPT. Furthermore, the volatiles contained in the RAPT infusion were extracted by three pretreatment methods (HS-SPME, SBSE, and SAFE) and identified using GC-O-MS. According to the odor activity value, 28 of 66 compounds were categorized as aroma-active compounds. Aroma recombination and omission experiments showed that "fatty", "green", "fruity", and "floral" are considered to be the main aroma attributes of RAPT infusion with a strong relationship with 1-octen-3-one, 1-octen-3-ol, (E)-2-octenal, ß-ionone, linalool, etc. This study will contribute a better understanding of the mechanism of the RAPT steeping process and volatile generation.

Characterization of key aroma compounds in low-salt fermented sour fish by gas chromatography-mass spectrometry, odor activity values, aroma recombination and omission experiments.

In this study, key aroma compounds of low-salt fermented sour fish were characterized using headspace solid-phase micro extraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS), odor activity values (OAV) and aroma recombination and omission experiments. Eighty-eight volatile compounds, including esters, aldehydes, alcohols, acids, furans and pyrazines, were identified by HS-SPME-GC-MS. Eighteen aroma-active compounds were quantified by employing calculation of OAV greater than 1. A recombination aroma model prepared using aroma-active compounds based on the odorless fish matrix sensorially matched the aroma of fermented sour fish with a score of 4.5 out of 5. The omission experiment showed that 7 out of 18 compounds had a significant contribution to the overall aroma (P < 0.05). The key aroma compounds of fermented sour fish were concluded to be ethyl acetate (OAV = 189), ethyl hexanoate (OAV = 66), isoamyl acetate (OAV = 424), ethyl butyrate (OAV = 26), hexanal (OAV = 49), 1-hexadecanal (OAV = 14) and 2-pentylfuran (OAV = 13).

Assessing the contribution of odor-active compounds in icewine considering odor mixture-induced interactions through gas chromatography-olfactometry and Olfactoscan.

The sensory impact of odor-active compounds on icewine aroma could be influenced by perceptual interactions with other odor-active compounds. The aim of this study was to establish an approach to evaluate the contribution of odor-active compounds found in icewine considering mixture-induced perceptual interactions. By comparing the impact of key odorants detected in icewine following a gas chromatography-olfactometry approach with an Olfactoscan-based methodology using a background odor of icewine, 69 odor zones were detected, and their related compounds were further identified. The results revealed that icewine background odor could exert odor masking or enhancement on key odorants when they are considered in the complex wine aroma buffer. Several compounds can induce qualitative changes in the overall wine aroma. This study underlined the efficiency of Olfactoscan-like approaches to screen for the real impact of key odorants and to pinpoint specific compounds that could be highly influential once embedded in the aroma buffer.

Qualitative Screening of Volatile Thiols in Wine by Selective Silver Ion Solid-Phase Extraction with Heart-Cutting Multidimensional Gas Chromatography Mass Spectrometry/Olfactometry.

The chemical analysis of odorous volatile thiols is intrinsically challenging. Substantial progress has been made in quantitative analysis of targeted thiols at ultra-trace concentrations (ng/L), but lesser analytical attention has been given to the qualitative screening of unknown thiols. This work presents a solid-phase extraction (SPE) method using a silver ion (Ag+)-based sorbent to isolate volatile thiols from red wine. This proposed Ag+ SPE method was effective (recovery: 87-101% for four non-furan thiols and 35-49% for two furan thiols), simple, safe, and greatly reduced artifacts, testifying to its suitability as the sample preparation protocol for a qualitative screening experiment. Separation and detection were conducted using heart-cutting multidimensional gas chromatography coupled to mass spectrometry/olfactometry (H/C MDGC-MS/O). Key parameters including H/C width, main host oven temperature, and cryogenic trapping temperature were investigated for optimal instrument performance. The developed Ag+ SPE H/C MDGC-MS/O strategy was readily applicable for qualitative screening of odorous volatile thiols in wine, as demonstrated by two case studies.

Identification of aroma-active compounds responsible for the floral and sweet odors of Congou black teas using gas chromatography-mass spectrometry/olfactometry, odor activity value, and chemometrics.

BACKGROUND: Floral and sweet odors are two typical characteristic aromas of Congou black tea, but their aroma-active compounds are still unclear. Characterizing the key aroma-active compounds can provide a theoretical foundation for the practical aroma quality evaluation of Congou black tea and directional processing technology of high-quality black tea with floral or sweet odors. Gas chromatography-olfactometry (GC-O) combined with odor activity value (OAV) is often used to screen key aroma-active substances, but the interaction between aroma components and their impact on the overall sensory quality is ignored. Therefore, in this study, OAV combined with variable importance in projection (VIP) and Spearman correlation analysis (SCA) were used to characterize the aroma-active components of Congou black teas with floral and sweet odors. RESULTS: Eighty-five volatiles were identified in these samples using gas chromatography-mass spectrometry (GC-MS). Twenty-three compounds were identified as potential markers for the floral and sweet odors of Congou black teas from orthogonal partial least squares discriminant analysis (OPLS-DA). Eighteen compounds were selected as candidate aroma compounds based on GC-O analysis and OAV calculations. In addition, 26 compounds were screened as crucial aroma compounds based on SCA. Finally, 19 compounds were evaluated as key aroma compounds by the comprehensive evaluation of VIP, OAV, and SCA. Terpenoids are the main active compounds that contribute to the floral odor of Congou black tea, whereas aldehydes are the key compounds for the sweet odor. CONCLUSION: The proposed method can effectively screen the aroma-active compounds and can be used for comprehensive quality control of products. © 2022 Society of Chemical Industry.

A Narrative Review of the Current Knowledge on Fruit Active Aroma Using Gas Chromatography-Olfactometry (GC-O) Analysis.

Fruit aroma, a mixture of chemical compounds with odor, is a strong attractant derived from a complex mixture of different amounts and intensities (threshold) of chemical compounds found in fruits. The odor-producing compounds of fruit aroma are derived from carbohydrates, lipids, phenolic compounds, and mono- and sesquiterpenes, among others. The identification of compounds responsible for fruit aroma is usually conducted using gas chromatography coupled with olfactometry (GC-O). This technique separates the chemical compounds from the aroma of foods using a chromatographic column and divides the resultant outflow between the physical detector and a testing outlet (sniffing port). Trained judges describe the perceived odor in terms of the intensity of the odor zones perceived according to their training method. Moreover, the use of GC-O coupled with a mass detector (GC-MS-O) allows for the retrieval of chemical information such as identification and quantification of compounds, which can be correlated to sensory information. This review aimed to demonstrate the application of GC-MS-O in the identification of precursor compounds in fruit aroma, considering important factors for the application, main results, and most recent advances in this field.

Toxicological assessment method for evaluating the occupational risk of dynamic olfactometry assessors.

The paper aims to propose a new method to evaluate the occupational exposure risk for examiners involved in dynamic olfactometry. Indeed, examiners are possibly exposed to hazardous pollutants potentially present in odorous samples. A standardized method to evaluate the examiners' occupational safety is not yet available and the existing models present some critical aspect if applied to real odorous samples (no uniform reference concentrations applied and presence of compounds for which no toxicity threshold is available). A deepening of assessment procedure to evaluate the occupation exposure risk for olfactometric assessors is necessary. This paper proposes a standardized approach for risk assessment in dynamic olfactometry. The proposed approach allows the quantification synthetic and conservative risk indices. In this model, the use of the hazard index for the odorous mixture was proposed to assess the non-carcinogenic risk; the calculation of the inhalation risk was applied to estimate the carcinogenic risk. Different databases can be used to retrieve proper occupational exposure limits, according to the proposed hierarchical basis. These implementations allow obtaining the complete characterization of real samples which can be used to calculate the minimum dilution factor for protecting the panellists' health.

Non-carcinogenic occupational exposure risk related to foundry emissions: focus on the workers involved in olfactometric assessments.

The scope of this work is the evaluation of the non-carcinogenic occupational risk related to foundry emissions, focusing on the category of workers involved in olfactometric assessments. Odor pollution from industrial activities such as foundries is a serious environmental concern. Sensorial techniques (e.g. dynamic olfactometry, EN13725:2003) currently represent the preferred method for odor emission characterization. During olfactometric analyses, human assessors are directly exposed to the odor at increasing concentrations, thus requiring the assessment of the associated exposure risk to guarantee workers' safety. This paper presents an investigation aiming to produce an inventory of compounds emitted from foundries together with their odor thresholds and toxicological limits (TLVs), with the final objective to propose a procedure for ensuring workers' safety during olfactometric analyses. Looking at the database resulting from this study, among the >100 compounds emitted by foundries, 8 have a maximum concentration above their TLV. Among those, ammonia, H2S, phenol, toluene and trimethylamine, produce an odor stimulus before they reach a toxic concentration, thus not representing a risk for olfactometric workers. Benzene, formaldehyde and SO2 are identified as the most critical compounds because they may reach toxic concentrations in foundry emissions, and they start being perceived by humans above their TLV. The proposed procedure entails a minimum dilution factor of 27'000 to be applied to odor samples analyzed by olfactometry, which however might result inapplicable in practical cases, thus pointing out the necessity to adopt chemical measurements to investigate specifically the concentration of the most critical compounds identified in this study.

Chemical fingerprinting strategies based on comprehensive two-dimensional gas chromatography combined with gas chromatography-olfactometry to capture the unique signature of Piemonte peppermint essential oil (Mentha x piperita var Italo-Mitcham).

Accurate, reliable, and informative mapping of untargeted and targeted components across many samples is here performed by combining off-line GC-Olfactometry (GC-O) and comprehensive two-dimensional gas chromatography (GC×GC) coupled to time-of-flight mass spectrometry with variable ionization energy (TOF MS featuring Tandem Ionization™). In particular, untargeted and targeted (UT) features patterns are processed by chromatographic fingerprinting, giving differential priority to potent odorants' retention-times regions. Distinguishing peppermint essential oil (EO) from Piedmont (Italy - Mentha × piperita L. var. Italo-Mitcham - Menta di Pancalieri EO), with its unique sensory fingerprint (i.e., freshness and long-lasting sweetness), from high-quality peppermint EOs produced in other areas poses a great challenge. Chromatographic UT fingerprinting provided a great chemical dimensionality by mapping more than 350 peak-regions at 70 eV and 135 at 12 eV. From them, 95 components were identified and responses compared to available literature. Then, potent odorants, detected by GC-O using the aroma extraction dilution analysis (AEDA), were tracked over the chromatographic space and tentatively identified. With the highest flavor dilution (FD), 1,8-cineole (eucalyptus, fresh, camphoraceous); menthone (minty, herbaceous); and menthofuran (minty, musty, petroleum-like) were highlighted. Responsible for creamy and coumarinic notes were the diasteroisomers of (3,6)-dimethyl-4,5,6,7-tetrahydrobenzo[b]-furan-2(3H)-one (i.e., menthofurolactones), detected in higher relative abundance in Pancalieri EOs. By prioritizing the investigation of volatiles on higher LogFD retention regions, including 131 untargeted/targeted features, Pancalieri EOs were separately clustered from United States samples. Besides pre-targeted analytes, additional untargeted features were post-processed for identification within marker chemicals. Myrtenyl methyl ether, ethyl 3-methyl butanoate, propyl-2-methylbutanoate, and (E)-2-hexenal were putatively identified. Of the "unknown - knowns" with diagnostic roles, all metadata were collected including low energy spectra at 12 eV, which were found to be highly complementary to 70 eV spectra.

Characterization of key odor-active compounds in sweet Petit Manseng (Vitis vinifera L.) wine by gas chromatography-olfactometry, aroma reconstitution, and omission tests.

Petit Manseng (Vitis vinifera L.) has become a popular variety in China for the production of semisweet and sweet wines. However, few studies focused on investigating the molecular odor code of its key odorants. In this study, the key odor-active compounds of Chinese sweet Petit Manseng wine were identified by gas chromatography-olfactometry (GC-O) and gas chromatography-mass spectrometry (GC-MS). Fifty-five odorous zones were sniffed and identified by application of aroma extraction dilution analysis on a distillate prepared by liquid-liquid extraction and solvent-assisted flavor evaporation. Among them, isoamyl alcohol, ethyl octanoate, isovaleric acid, (E)-ß-damascenone, and phenylethanol particularly displayed with highest flavor dilution factors above 1024. The quantification of volatiles by headspace solid-phase microextraction coupled with GC-MS and GC coupled with triple quadrupole MS/MS and a calculation of odor activity values (OAVs) indicated 23 volatiles with OAVs above 1. Ethyl hexanoate showed the highest OAV with 208.8, followed by (E)-ß-damascenone (189.0), 3-mercaptohexanol (60.3), isoamyl acetate (45.4), and furaneol (40.1). The aroma of the sweet wine was successfully reconstituted by combining 42 aroma compounds in a model wine solution. 3-Mercaptohexanol, (E)-ß-damascenone, furaneol, γ-octalactone + γ-decalactone + γ-hexalactone, and ethyl cinnamate had important influence on the aroma of sweet Petit Manseng wine assessed by omission tests. Moreover, the discrimination of wines from three regions was successfully achieved by partial least squares discriminant analysis based on quantitative results of key odorants. 3-Mercaptohexanol was considered as the most responsible for the region discrimination and had highest concentrations in Petit Manseng wines from Jiaodong Peninsula. PRACTICAL APPLICATION: Understanding of the knowledge in key odorants of Petit Manseng wines could be useful to improve wine quality through viticultural and enological practices.

Characterization of the key aroma compounds in Laoshan green teas by application of odour activity value (OAV), gas chromatography-mass spectrometry-olfactometry (GC-MS-O) and comprehensive two-dimensional gas chromatography mass spectrometry (GC × GC-qMS).

To investigate the key aroma compounds in Laoshan green teas (Huangshan (S1), Changling (S2), and Fangling (S3)), gas chromatography-mass spectrometry-olfactometry (GC-MS-O), a flame photometric detector (FPD), odor activity value (OAV), and comprehensive two-dimensional gas chromatography mass spectrometry (GC × GC-qMS) were employed. A total of 50 aroma compounds were perceived and 24 compounds were identified as important compounds related to OAV, such as dimethyl sulfide (OAV: 126-146), skatole (OAV: 27-50), furaneol (OAV: 8-27), (Z)-jasmone (OAV: 16-23), 2-methylbutanal (OAV: 15-22), and 3-methylbutanal (OAV: 68-87). Furthermore, the S-curve method was used to research the effect of aroma compounds on the threshold of aroma recombination (AR). The AR thresholds decreased from 3.8 mL to 0.45, 0.66, 0.93, 0.95, 0.75, 1.09, 3.01, and 2.57 mL after addition of eight compounds (skatole, furaneol, (Z)-jasmone, α-damascenone, sclareololide, dihydroactinidiolide, vanillin, and δ-valerolactone), indicating that those compounds (OAV >1) were contributors to the overall aroma of Laoshan teas.

Identification of key odorants in honeysuckle by headspace-solid phase microextraction and solvent-assisted flavour evaporation with gas chromatography-mass spectrometry and gas chromatograph-olfactometry in combination with chemometrics.

At present, the identification of honeysuckle aroma depends on experienced tasters, which results in inconsistencies due to human error. The key odorants have the potential to distinguish the different species and evaluate the quality of honeysuckle. Hence, in this study, a more scientific approach was applied to distinguish various honeysuckles. The volatile compounds of different species and parts of honeysuckle were separately extracted by headspace-solid phase microextraction (HS-SPME) and solvent assisted flavor evaporation (SAFE). Compounds with greater volatility such as aldehydes, limonene, γ-terpinene, and terpinolene were preferentially extracted by HS-SPME. As a complementary extraction method to HS-SPME, SAFE was found to recover comparatively more polar compounds such as eugenol, decanoic acid, and vanillin. Subsequently, key odorants with the highest flavour dilution (FD) factors were detected by aroma extract dilution analysis (AEDA). These were benzaldehyde, 4-ethylphenol, decanoic acid, vanillin, 3-methyl-2-butenal, and ß-ionone in honeysuckle flowers and γ-octalactone, 4-ethyl phenol, and vanillin in honeysuckle stem. Finally, principal component analysis (PCA) was conducted to analyze not only the key odorants of species and parts of honeysuckle but also their different origins. The results of PCA suggested that the species of honeysuckle contributed much more to variations in aroma rather than their origins. In conclusion, the application of the key odorants combined with PCA was demonstrated as a valid approach to differentiate species, origins, and parts of honeysuckle.

Characterization of Odor-Active Compounds, Polyphenols, and Fatty Acids in Coffee Silverskin.

For the first time the volatile fraction of coffee silverskin has been studied focusing on odor-active compounds detected by gas chromatography-olfactometry/flame ionization detector (GC-O/FID) system. Two approaches, namely headspace (HS) analysis by solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) and odor-active compounds analysis by gas chromatography-olfactometry/flame ionization detector (GC-O/FID), have been employed to fully characterize the aroma profile of this by-product. This work also provided an entire characterization of the bioactive compounds present in coffee silverskin, including alkaloids, chlorogenic acids, phenolic acids, flavonoids, and secoiridoids, by using different extraction procedures and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) system. Coffee silverskin was shown to be a good source of caffeine and chlorogenic acids but also of phenolic acids and flavonoids. In addition, the fatty acid composition of the coffee silverskin was established by GC-FID system. The results from this research could contribute to the development of innovative applications and reuses of coffee silverskin, an interesting resource with a high potential to be tapped by the food and nutraceutical sector, and possibly also in the cosmetics and perfumery.

Characterization of the key aroma compounds in Longjing tea using stir bar sorptive extraction (SBSE) combined with gas chromatography-mass spectrometry (GC-MS), gas chromatography-olfactometry (GC-O), odor activity value (OAV), and aroma recombination.

Longjing tea is the most famous premium green tea, and is regarded as the national tea in China, with its attractive aroma contributing as a prime factor for its general acceptability; however, its key aroma compounds are essentially unknown. In the present study, volatile compounds from Longjing tea were extracted and examined using stir bar sorptive extraction (SBSE) combined with gas chromatography-mass spectrometry (GC-MS). Data obtained from the present study revealed that 151 volatile compounds from 16 different chemical classes were identified by GC-MS analysis. Enols (8096 µg/kg), alkanes (6744 µg/kg), aldehydes (6442 µg/kg), and esters (6161 µg/kg) were the four major chemical classes and accounted for 54% of the total content of volatile compounds. Geraniol (6736 µg/kg) was the most abundant volatile compound in Longjing tea, followed by hexanal (1876 µg/kg) and ß-ionone (1837 µg/kg). Moreover, 14 volatile compounds were distinguished as the key aroma compounds of Longjing tea based on gas chromatography-olfactometry (GC-O) analysis, odor activity value (OAV) calculations, and a preliminary aroma recombination experiment, including 2-methyl butyraldehyde, dimethyl sulfoxide, heptanal, benzaldehyde, 1-octen-3-ol, (E, E)-2,4-heptadienal, benzeneacetaldehyde, linalool oxide I, (E, E)-3,5-octadien-2-one, linalool, nonanal, methyl salicylate, geraniol, and ß-ionone. This is the first comprehensive report describing the aroma characterizations and the key aroma compounds in Longjing tea using SBSE/GC-MS. The findings from this study contribute to the scientific elucidation of the chemical basis for the aromatic qualities of Longjing tea.